Roofshield is a unique three layer breather membrane, intended for use as a pitched roof underlay and is fixed
beneath tiles and slates. It provides a secondary barrier to the ingress of rain, wind and snow.
It has a low vapour resistance and is air permeable, eliminating the incidence of interstitial condensation in pitched roofs It also negates the need for a vapour control layer or air barrier fixed at ceiling level
Roofshield breather membrane eliminates the need for low and high level ventilation, no need for vent components and the labour costs to install them.
ROOFSHIELD UNIQUE FEATURES & BENEFITS INCLUDE:
• Water resistant.
• Low vapour resistance.
• Air permeable.
• UV resistant.
• Hydrophobically treated.
• Supplied 1m x 50m rolls.
• 350mm tile batten spacing.
• Compatible with reputable UK timber treatments.
• Warm & Cold roof applications.
• Eliminates low & high level ventilation.
• No vapour control layer required.
• BBA Approved.
• A cost effective solution to complying with Building Regulations.
Issues that a building designer or project manager ought to consider include:
1. Resistance to water vapour – ‘the lower the better’
To reduce condensation problems, the underlay needs to breathe. Resistance to water vapour is important when assessing the risk of condensation. The lower the vapour resistance of a breather membrane the further it inhibits the formation of condensation.
The present legislation requires that a breather membrane must have a vapour resistance of less than 0.25 MNs/g, Roofshield has a vapour resistance of 0.09 MNs/g and is classified as a low vapour resistant underlay.
2. Air Permeability
Roofshield, in addition to having a low vapour resistance is also air permeable. Industry research concluded that air permeability combined with low vapour resistance, further inhibits the
formation of condensation in a pitched roof.
3. Water resistant when fully supported – ‘some breather membranes can leak’
Early camping experiences have proven that if you touch the inside face of a canvas tent on a rainy day, the surface tension is broken and rainwater comes in. The same is also true for some
types of breather membranes which need to be pulled taught over the rafters, otherwise water may penetrate through where the membrane touches the supports. Roofshield can be laid in direct contact with rafters, timber sarking boards or insulation with no loss of its waterproofing properties.
4. ‘Ventilation to the underside of underlay not required in warm or cold roof applications’
The BBA Certificate confirms that the membrane may be used without a ventilated airspace below the underlay in cold or warm roofs (see manufacturers guidelines).